3.8.4.3 Renewable Energy Conversion Technologies

Natural energy flows vary from location to location, and make the techno-economic
performance of renewable energy conversion highly site-specific. Intermittent
sources such as wind, solar, tidal, and wave energy require back-up if not grid
connected, while large penetration into grids may eventually require storage
and/or back-up to guarantee reliable supply. Therefore, it is difficult to generalize
costs and potentials.

3.8.4.3.1 Hydropower

Hydroelectricity remains the most developed renewable resource worldwide with
global theoretical potential ranges from 36,000 to 44,000TWh/yr (World Atlas,
1998). Approximately 65% of the technical hydro potential has been developed
in Western Europe, and 76% in the USA. This indicates a limit caused by societal
and environmental barriers. For many developing countries the total technical
potential, based on simplified engineering and economic criteria with few environmental
considerations, has not been fully measured. The economic potential resulting
from detailed geological and technical evaluations, but including social and
environmental issues, i s difficult to establish because these parameters are
strongly driven by societal preferences inherently uncertain and difficult to
predict. A rate of utilization between 40% and 60% of a regions technical
potential is therefore a reasonable assumption and leads to a global economic
hydro-electricity potential of 7,000 to 9,000TWh/yr (see Table
3.30).

Numerous small (<10MW), mini (<1MW) and micro (<100kW) scale hydro
schemes with low environmental impacts continue to be developed globally. The
extent of this resource, particularly in developing countries such as Nepal,
Oceania, and China, is unknown but likely to be of significance to rural communities
currently without electricity.

Large-scale hydropower plant developments can have high environmental and social
costs such as loss of fertile land, methane generation from flooded vegetation,
and displacement of local communities (Moomaw et al., 1999b). At the 18,200
MW Three Gorges dam under construction in China, 1.2 million people have been
moved to other locations. Another limitation to further development is the high
up-front capital investment which the recently privatized power industries are
unlikely to accept because of the low rates of return.

The remote locations of many potential hydro sites result in high transmission
costs. Development of medium (<50MW) to small (<10MW) scale projects closer
to demand centres will continue. In countries where government or aid assistance
is provided to overcome the higher investment costs/MW at this scale, power
generation costs around US$0.065/kWh will result (UK DTI, 1999). Mini- and micro-hydro
low head turbines are under development but generating costs at this scale are
likely to remain high, partly as a result of the cost of the intake structure
needed to withstand river flood conditions. Even at this small scale, environmental
and ecological effects often result from taking water from a stream or small
river and discharging it back again, even after only a short distance.

Table 3.30: Annual large hydroelectric
development potential (TWh/yr)

Theoretical potential

Technological potential

Economic potential

TWha

TWhb

TWha

TWhb

TWha

TWhb

Africa

3,307

3,633

1,896

1,589

815

866

North America

5,817

5,752

1,509

1,007

912

957

Latin America

7,533

8,800

2,868

3,891

1,198

2,475

Asia (excluding former USSR)

15,823

14,138

4,287

4,096

1,868

2,444

Australasia

591

592

201

206

106

168

Europe

3,128

3,042

1,190

942

774

702

Former USSR

3,583

3,940

1,992

2,105

1,288

1,093

World

39,784

39,899

13,945

13,839

6,964

8,708

a World Atlas, 1999b International Water Power & Dam Construction, 1997